Abstract Despite recent advances in implantable biomedical devices, the utilization of wireless power delivery continues to be a challenge due to anatomical size constraints that limit sufficient power transfer. In addition to pacemakers, implantable stimulators, including neuromodulation devices used for spinal cord, deep brain, and peripheral nerve stimulation, are confined by the same lead-based architecture. Thus, developing wireless power transfer for implantable devices, including the pacemaker, has the potential to mitigate a host of device- related complications. A primary challenge in inductively powered biomedical devices remains in developing a micro-scale receiver antenna with sufficient power output while minimizing transmitter power consumption over an anatomically and wirelessly feasible range. Eliminating the pacing leads, bulky batteries, fixation-associated mechanical burden, and repeated procedures for battery replacement and device retraction remains an unmet clinical need. In this context, we seek to advance a long-range inductively powered wireless and batteryless micro ()-system with sufficient power for pacing functionality. Our encouraging preliminary results support the feasibility of a pacing system with a subcutaneous unit and micro-scale pacer unit to induce sufficient power transfer for ex vivo pacing to a porcine heart. We hereby address the fundamental constraints of in vivo long- range pacing using an intravascular micro-pacing system. Our objective is to integrate advanced antenna and circuit design into a pacer system to enable intravascular deployment of wirelessly powered -pacer to the anterior cardiac vein (ACV) for pacing. Our goal is to eliminate the device fixation- and lead-related mechanical complications for optimal power transfer efficiency. To deliver our objective, we have three aims. In Aim 1, we will demonstrate the fundamental -antenna design and fabrication to enhance power transfer efficiency. In Aim 2, we will integrate CMOS technology and the novel parylene-on-oil encapsulation to enable intravascular deployment. In Aim 3, we will demonstrate the -pacer for real-time intravascular pacing in our pre-clinical model. Successful deployment of this wireless power transmission system provides the theoretical and experimental framework to overcome the anatomical size constraints that limit sufficient power transfer with translational implications for both cardiac and non-cardiac stimulation.